Robot Earthworm Inches Forward

Robots are generally made of hard materials — metal or plastic -– and can't squeeze into irregular spaces. That may change with a robot that moves the way earthworms do.

Such a wiggly robot could get into tight spaces in a disaster zone to look for survivors or wriggle into pipes for repairs or cleaning. They would also be able to walk over terrain that frustrates wheeled –- or even legged –- robots.

The robot, designed by a team at the Massachusetts Institute of Technology, Harvard University and Seoul National University, is called "Meshworm," and mimicks the movement of an earthworm. These animals have muscle fibers that encircling their bodies like belts, while another set lines up parallel along their length. A worm stretches a bit of its body forward at the front and pulls it in at the back, creating a ripple that moves the worm. That expansion and contraction of the muscles is called peristalsis.

Meshworm's "muscles" are made of a mesh of shape-memory alloy. The metal bends and then "remembers" its original shape when heated. The scientists wound the wire around a tube, creating beltlike segments simliar those of a worm. More wires were run the length of the robot. They then ran a small current through the beltlike segments, causing the wires to contract, squeezing the tube and propelling the robot forward. A current directed to the longitudinal wires caused the Meshworm to move side-to-side.

By using the metals to mimic the muscles, engineers avoid the problems of motors and actuators, which can be small but are difficult to build below a certain size.

Other methods for propelling robotic worms could include compressed air or even chemical signals similar to amoebas. But compressed air requires pumps, which are also hard to make small, and using chemical signals means that the robot needs specific compounds to trigger the motion. Meshbot operates independently of that.

Another big plus is durability. The MIT team said its robot can handle being smacked with a hammer, which could be extremely important in disaster areas.

The details of the work appeared in the journal IEEE/ASME Transactions on Mechatronics.